This invention relates to catalyst systems useful in producing flexible polyurethane polyester foams. More particularly, it relates to catalysts for producing low-odor foams which are not prone to discoloration, and which have a low volatile organic chemical content.
Flexible polyurethane polyester foams require unique catalysts to produce stable low-color foams. These catalysts are normally weak blowing catalysts such as n-ethyl morpholine and N-methyl morpholine. These weak blowing catalysts have very high vapor pressure. This results in high amounts of odor in the foam and in the production area. Since these catalysts are relatively weak in activity, relatively large amounts are required to produce stable foam at a reasonable production rate. The large amount of such catalyst that is required to be used further compounds the odor problems associated with the use of these catalysts. The use of strong gel catalysts such as 1,4-diazabicyclo[2,2,2]octane is not normally practiced since the amount required to give the proper initiation or cream time also results in tight foam that shrinks on storage. The above-mentioned morpholine-based catalysts produce white foams and color stable foams when employing certain reactant dyes.
Another weak blowing catalyst, methoxyethyl morpholine, may be used to produce ester foams, however the amount required is more twice that of N-ethyl morpholine. The foams produced are lower in odor due to the lower vapor pressure of methoxyethylmorpholine, but unfortunately the foams discolor or turn pink during curing. Combinations of gel catalysts such as N,N-dimethylpiperazine and weak blowing catalysts such as Dimorpholinodiethylether have been practiced. Unfortunately these combinations produce foams that pink. Additionally, N,N-dimethylpiperazine has a high vapor pressure. While the use of N,N-dimethylpiperazine does produce lower odor foams than N-ethylmorpholine or N-methylmorpholine, this catalyst combination still produces a significant amount of VOC and odor in the foam production area. The use of a strong gel catalyst such as N,N-Bis[3-(dimethylamino)propyl]formamide can be used to replace the highly volatile dimethylpiperazine. Unfortunately the use of N,N-Bis[3-(dimethylamino)propyl]formamide as the sole catalyst produces a tight foam that displays the xe2x80x9cfinger nailxe2x80x9d effect, whereby the foam does not recover completely following its indention with a fingernail or other sharp object.
We have discovered that catalyst compositions which comprise combinations of a weak blowing catalyst, such as methoxyethylmorpholine, and a strong gelling catalyst, such as N,N-bis[3-(dimethylamino)propyl]formamide, produce color-stable foams with reactant dyes, and produce foams that do not take on a pink shade of color or scorch in the absence of dyes, while being possessive of a reduced level of odors and emissions during the foaming process over foams using prior-art catalysts. Optionally, a strong blowing catalyst such as 2,2xe2x80x2-oxybis(N,N-dimethylethanamine) and/or 2-((2-(dimethylamino)ethoxy)ethyl)methyl-amino)-ethanol can be incorporated to adjust initiation and rise time. The incorporation of such optional strong blowing catalysts further reduces odors and VOC""s due to reduced amounts of catalyst needed to achieve the desired reactivity. 2,2xe2x80x2-oxybis(N,N-dimethylethanamine) is available from Huntsman Petrochemical Corporation of Austin, Tex. under the trade name JEFFCAT(copyright) ZF-20 catalyst, and or 2-((2-(dimethylamino)ethoxy)ethyl)methyl-amino)-ethanol is available from Huntsman Petrochemical Corporation of Austin, Tex. under the trade name JEFFCAT(copyright) ZF-10 catalyst.